STEER/AliTOFPIDResponse.cxx

   1 /**************************************************************************
   2  * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. *
   3  *                                                                        *
   4  * Author: The ALICE Off-line Project.                                    *
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  15
  16 //-----------------------------------------------------------------//
  17 //                                                                 //
  18 //           Implementation of the TOF PID class                   //
  19 //      Origin: Iouri Belikov, CERN, Jouri.Belikov@cern.ch         //
  20 //                                                                 //
  21 //-----------------------------------------------------------------//
  22
  23 #include "TMath.h"
  24 #include "AliLog.h"
  25
  26 #include "AliTOFPIDResponse.h"
  27
  28 ClassImp(AliTOFPIDResponse)
  29
  30 //_________________________________________________________________________
  31 AliTOFPIDResponse::AliTOFPIDResponse():
  32   fSigma(0),
  33   fPmax(0),         // zero at 0.5 GeV/c for pp
  34   fTime0(0)
  35 {
  36   // Reset T0 info
  37   ResetT0info();
  38   SetMomBoundary();
  39 }
  40 //_________________________________________________________________________
  41 AliTOFPIDResponse::AliTOFPIDResponse(Double_t *param):
  42   fSigma(param[0]),
  43   fPmax(0),          // zero at 0.5 GeV/c for pp
  44   fTime0(0)
  45 {
  46   //
  47   //  The main constructor
  48   //
  49   //
  50
  51   //fPmax=TMath::Exp(-0.5*3*3)/fSigma; // ~3 sigma at 0.5 GeV/c for PbPb
  52
  53   // Reset T0 info
  54   ResetT0info();
  55   SetMomBoundary();
  56 }
  57 //_________________________________________________________________________
  58 Double_t
  59 AliTOFPIDResponse::GetMismatchProbability(Double_t p, Double_t mass) const {
  60   //
  61   // Returns the probability of mismatching
  62   // assuming 1/(p*beta)^2 scaling
  63   //
  64   const Double_t km=0.5;                   // "reference" momentum (GeV/c)
  65
  66   Double_t ref2=km*km*km*km/(km*km + mass*mass);// "reference" (p*beta)^2
  67   Double_t p2beta2=p*p*p*p/(p*p + mass*mass);
  68
  69   return fPmax*ref2/p2beta2;
  70 }
  71 //_________________________________________________________________________
  72 Double_t AliTOFPIDResponse::GetExpectedSigma(Float_t mom, Float_t time, Float_t mass) const {
  73   //
  74   // Return the expected sigma of the PID signal for the specified
  75   // particle type.
  76   // If the operation is not possible, return a negative value.
  77   //
  78
  79   Double_t dpp=0.018*mass/mom;      //mean relative pt resolution;
  80
  81
  82   Double_t sigma = dpp*time/(1.+ mom*mom/(mass*mass));
  83
  84   Int_t index = GetMomBin(mom);
  85
  86   Double_t t0res = fT0resolution[index];
  87
  88   return TMath::Sqrt(sigma*sigma + 50.0*50.0/mom/mom + fSigma*fSigma + t0res*t0res);
  89
  90 }
  91 //_________________________________________________________________________
  92 Int_t AliTOFPIDResponse::GetMomBin(Float_t p) const{
  93   //
  94   // Returns the momentum bin index
  95   //
  96
  97   Int_t i=0;
  98   while(p > fPCutMin[i] && i < fNmomBins) i++;
  99   if(i > 0) i--;
 100
 101   return i;
 102 }
 103 //_________________________________________________________________________
 104 void AliTOFPIDResponse::SetMomBoundary(){
 105   //
 106   // Set boundaries for momentum bins
 107   //
 108
 109   fPCutMin[0] = 0.3;
 110   fPCutMin[1] = 0.5;
 111   fPCutMin[2] = 0.6;
 112   fPCutMin[3] = 0.7;
 113   fPCutMin[4] = 0.8;
 114   fPCutMin[5] = 0.9;
 115   fPCutMin[6] = 1;
 116   fPCutMin[7] = 1.2;
 117   fPCutMin[8] = 1.5;
 118   fPCutMin[9] = 2;
 119   fPCutMin[10] = 3;
 120 }
 121 //_________________________________________________________________________
 122 Float_t AliTOFPIDResponse::GetStartTime(Float_t mom) const {
 123   //
 124   // Returns event_time value as estimated by TOF combinatorial algorithm
 125   //
 126
 127   Int_t ibin = GetMomBin(mom);
 128   return GetT0bin(ibin);
 129
 130 }
 131 //_________________________________________________________________________
 132 Float_t AliTOFPIDResponse::GetStartTimeRes(Float_t mom) const {
 133   //
 134   // Returns event_time resolution as estimated by TOF combinatorial algorithm
 135   //
 136
 137   Int_t ibin = GetMomBin(mom);
 138   return GetT0binRes(ibin);
 139
 140 }